how to defin an item in the center code example

Example 1: align items center css

.parent_div
{
  display:flex;
  align-items:center;
}

Example 2: alignitems

/* Basic keywords */ 
align-items: normal; 
align-items: stretch; 

/* Positional alignment */ 
/* align-items does not take left and right values */
align-items: center; /* Pack items around the center */ 
align-items: start; /* Pack items from the start */ 
align-items: end; /* Pack items from the end */ 
align-items: flex-start; /* Pack flex items from the start */ 
align-items: flex-end; /* Pack flex items from the end */

/* Baseline alignment */
align-items: baseline; 
align-items: first baseline; 
align-items: last baseline; /* Overflow alignment (for positional alignment only) */ 
align-items: safe center; 
align-items: unsafe center; 

/* Global values */
align-items: inherit; 
align-items: initial; 
align-items: unset;